Many crops, such as vegetables or tree seedlings, are first grown in nursery beds rather than planted directly. When the seedlings have reached an adequate size, the seedlings are harvested and packaged for subsequent replanting. While seedlings may be harvested by hand, the process is extremely labor intensive. Another option is to use a harvesting machine to recover the seedlings from the nursery bed. One such harvester is disclosed in U.S. Pat. No. 4,326,590, entitled Plant-Harvesting Device for Use with Variable Crop Row Spacing, assigned to Weyerhaeuser Company, assignee of the present disclosure (“the '590 patent”). A harvester such as the one in the '590 patent lifts the seedlings from the nursery bed, performs processing such as root untangling and soil removal on the seedlings, and provides the seedlings for packaging. Once packaged, the seedlings are often sold to customers or otherwise transferred to other locations for planting.
A persistent problem in packaging seedlings harvested through automated processes is in quantifying the number of seedlings contained in each package. It is desirable to have the same number of seedlings in each package, or at least to know exactly how many seedlings are in each package. For example, it is common to offer packages containing one thousand seedlings each for sale. Accuracy in the count of seedlings in each package is obviously important, as planting crews commonly pay workers by the number of seedlings planted. Further, if package counts vary, then planters will often count the seedlings in the package before planting, which can lead to harm to the seedling roots. Often, more seedlings are packed into each package than contracted for, merely to avoid problems reported by the purchaser.
Obtaining an accurate count of harvested seedlings is difficult for many reasons. One reason is that, given the vast number of seedlings in a given nursery bed, it is likely that the seedlings are not evenly distributed throughout the bed. Another reason is that not all of the seedlings will grow at the same rate. While a majority of the seedlings might be of an adequate size for harvesting, other seedlings may be too small, and would need to be culled or otherwise not included in the package count if they were harvested along with the good seedlings.
Various attempts have been made to count seedlings as they sequentially move past an automated counter. However, each of these seedling counters suffer from various deficiencies. For example, existing seedling counters tend to undercount by counting seedlings that are too close to one another while passing through the counter as a single seedling. As another example, existing seedling counters tend to overcount by failing to properly exclude cull seedlings from the count, or by counting branches, leaves, needles, or other debris passing through the counter as seedlings. As yet another example, existing seedling counters tend to lose accuracy when seedlings do not pass through the counter in an expected orientation. What is needed is a seedling counter that can overcome these limitations to produce accurate seedling counts.